1. Field of the Invention
The present invention relates to an optically rewritable optical disc and to an apparatus and method for reading addresses prewritten to the optical disc.
2. Description of Related Art
DVD-RAM, CD-RW, and MD are examples of user-recordable optical discs that have become available in the last few years. This type of recordable optical disc has grooves formed along a spiral or plural concentric tracks with a phase change material or magneto-optical material formed on the groove surface. Addresses for specifying a particular location on the disc are also pre-recorded to the tracks using rewritable marks. This type of address is described in Japanese Patent Laid-Open Publication (kokai) H8-315426.
Kokai H8-315426 describes providing discontinuities in the grooves and using these discontinuous parts for forming a pattern corresponding to the address signal. A pattern corresponding to the address signal is a binary signal that inverts at each discontinuity, an on/off signal used for generating an ATIP (Absolute Time Pregroove) signal. The discontinuities are therefore used simply as a signal indicating presence or absence.
(Technical Problem to be Solved)
More address values and a method for more efficiently assigning address values is needed in order to create an optical disc with an even higher recording density. In an optical disc according to the related art, however, the discontinuities are nothing more than a trigger signal for signal inversion and can carry only one piece of information (trigger data). Numerous marks are therefore required.
Furthermore, the approximate location of a track can be detected with the ATIP signal, but the position where recording starts cannot be precisely determined. This means that when appending a new recording after recording once, or when overwriting data in the middle of a previous recording, new data may be recorded over previously recorded data that is still necessary. Crosstalk also occurs more easily when the track pitch is reduced.
The present invention is directed to a solution for these problems and provides an optical disc wherein discontinuities or modifications are formed in the grooves and two or more meanings are imparted to the discontinuities or modifications in order to provide address information more efficiently.
A further object of the invention is to provide an optical disc whereby the positioning precision of the recording start point can be increased.
A yet further object of the invention is to provide an optical disc enabling the track pitch to be reduced.
A yet further object of the invention is to provide an optical disc that is recordable and playable with full CLV (constant linear velocity) control.
A yet further object of the invention is to provide an apparatus and method of simple design for accurately reading address information from an optical disc having address information containing two or more meanings imparted to discontinuities or modifications formed in the grooves.
The invention as described in claim 1 is a rewritable optical disc with a spiral or concentric track comprising:
a groove formed with a sinusoidal wobble along the track;
a sector block disposed along the track;
sectors formed by dividing each sector block into a plurality of parts;
a synchronization mark formed in the first sector in each sector block; and
positive marks or negative marks formed in sectors other than the first sector in each sector block;
each positive mark being a first groove discontinuity creating a discontinuity of a first width W1 in the track direction of the groove,
each negative mark being a second groove discontinuity creating a discontinuity of a second width W0 in the track direction of the groove, and
each synchronization mark being a third groove discontinuity creating a discontinuity of a third width Ws in the track direction.
The invention as described in claim 2 is an optical disc as described in claim 1, wherein the first, second, and third groove discontinuities have a mirror surface.
The invention as described in claim 3 is an optical disc as described in claim 1, wherein the first, second, and third groove discontinuities are formed in maximum amplitude parts of the wobble groove.
The invention as described in claim 4 is an optical disc as described in claim 1, wherein the first, second, and third groove discontinuities are formed in the minimum amplitude part of the wobble groove.
The invention as described in claim 5 is an optical disc as described in claim 1, wherein the first, second, and third widths W1, W0, and Ws are all longer than the longest mark contained in data recorded to a groove and less than or equal to xc2xd wobble period.
The invention as described in claim 6 is an optical disc as described in claim 1, wherein the first, second, and third widths W1, W0, and Ws are all longer than the longest mark contained in data recorded to a groove and less than or equal to xc2xc wobble period.
The invention as described in claim 7 is an optical disc as described in claim 1, wherein the ratio between first, second, and third widths W1, W0, and Ws is 1:2:4 where any one of widths W1, W0, and Ws is 1.
The invention as described in claim 8 is an optical disc as described in claim 1, wherein the ratio between first, second, and third widths W1, W0, and Ws is 2:1:4.
The invention as described in claim 9 is an optical disc as described in claim 1, wherein the first, second, and third widths W1, W0, and Ws are two bytes, one byte, and four bytes, respectively.
The invention as described in claim 10 is a rewritable optical disc with a spiral or concentric track comprising:
a groove formed with a sinusoidal wobble along the track;
a sector block disposed along the track;
sectors formed by dividing each sector block into a plurality of parts;
a synchronization mark formed in the first sector in each sector block; and
positive marks or negative marks formed in sectors other than the first sector in each sector block;
each positive mark, negative mark, and synchronization mark being formed as a groove top offset portion where the groove is locally offset in a first direction perpendicular to the track direction, a groove bottom offset portion where the groove is locally offset in a second direction perpendicular to the track direction, or a combination of groove bottom offset portions and groove top offset portions.
The invention as described in claim 11 is an optical disc as described in claim 10, wherein:
a positive mark is a groove top offset portion;
a negative mark is a groove bottom offset portion; and
a synchronization mark is a combination of a groove top offset portion and groove bottom offset portion.
The invention as described in claim 12 is an optical disc as described in claim 10, wherein the groove bottom offset portions and groove top offset portions are disposed at maximum amplitude parts of the wobble groove and are offset in a track center direction.
The invention as described in claim 13 is an optical disc as described in claim 10, wherein groove bottom offset portions and groove top offset portions of a synchronization mark are mutually adjacent at n+(xc2xd) wobble cycles (where n is a positive integer).
The invention as described in claim 14 is an optical disc as described in claim 13, wherein n is 0.
The invention as described in claim 15 is a rewritable optical disc with a spiral or concentric track comprising:
a groove formed with a sinusoidal wobble along the track;
a sector block disposed along the track;
sectors formed by dividing each sector block into a plurality of parts;
a synchronization mark formed in the first sector in each sector block; and
positive marks or negative marks formed in sectors other than the first sector in each sector block;
each positive mark, negative mark, and synchronization mark being formed by a groove ascending-phase inversion part for vertically phase inverting an approximately xc2xc wobble cycle part from a trough in the wobble groove, a groove descending-phase inversion part for vertically phase inverting an approximately xc2xc wobble cycle part from a peak in the wobble groove, or a combination of a groove ascending-phase inversion part and groove descending-phase inversion part.
The invention as described in claim 16 is an optical disc as described in claim 15, wherein a positive mark is formed by a groove ascending-phase inversion part, a negative mark is formed by a groove descending-phase inversion part, and a synchronization mark is formed by a combination of a groove descending-phase inversion part and groove ascending-phase inversion part.
The invention as described in claim 17 is an optical disc as described in claim 15, wherein both ends of said groove descending-phase inversion parts and groove ascending-phase inversion parts are a groove discontinuity.
The invention as described in claim 18 is an optical disc as described in claim 15, wherein both ends of said groove descending-phase inversion parts and groove ascending-phase inversion parts are an abruptly displaced groove.
The invention as described in claim 19 is a rewritable optical disc with a spiral or concentric track comprising:
a groove formed with a sinusoidal wobble along the track;
a sector block disposed along the track;
sectors formed by dividing each sector block into a plurality of parts;
a synchronization mark formed in the first sector in each sector block; and
positive marks or negative marks formed in sectors other than the first sector in each sector block;
each positive mark, negative mark, and synchronization mark being formed by a groove ascending-rectilinear portion connected to the wobble peak by forming the groove at a trough level from a trough in the wobble groove to an approximately xc2xc wobble cycle portion of the wobble groove, then abruptly changing to a peak level and forming the groove at the peak level in the next xc2xc wobble cycle portion,
a groove descending-rectilinear portion connected to the wobble trough by forming the groove at a peak level from a peak in the wobble groove to an approximately xc2xc wobble cycle portion of the wobble groove, then abruptly changing to a trough level and forming the groove at the trough level in the next xc2xc wobble cycle portion, or
a combination of a groove descending-rectilinear portion and groove ascending-rectilinear portion.
The invention as described in claim 20 is an optical disc as described in claim 19, wherein a positive mark is formed by a groove ascending-rectilinear portion, a negative mark is formed by a groove descending-rectilinear portion, and a synchronization mark is formed by a combination of a groove descending-rectilinear portion and groove ascending-rectilinear portion.
The invention as described in claim 21 is an optical disc as described in claim 19, wherein each positive mark, negative mark, and synchronization mark is formed by said groove ascending-rectilinear portion being repeated for a plurality of cycles of the wobbled groove, said groove descending-rectilinear portion being repeated for a plurality of cycles of the wobbled groove, or said combination of a groove descending-rectilinear portion and groove ascending-rectilinear portion being repeated for a plurality of cycles of the wobbled groove.
The invention as described in claim 22 is an optical disc as described in claim 21, wherein each positive mark is formed by said groove ascending-rectilinear portion being repeated for a plurality of cycles of the wobbled groove,
each negative mark is formed by said groove descending-rectilinear portion being repeated for a plurality of cycles of the wobbled groove, and
each synchronization mark is formed by said combination of a groove descending-rectilinear portion and groove ascending-rectilinear portion being repeated for a plurality of cycles of the wobbled groove.
The invention as described in claim 23 is an address reading apparatus for detecting synchronization marks, positive marks, and negative marks contained in an optical disc as described in claim 1 and accumulating 1 and 0 data obtained from positive marks and negative marks dispersedly contained in one sector block to read said sector block address, comprising:
an optical head (2) for emitting a laser beam to a track of the optical disc and detecting reflected light by means of two photodetectors separated along the track direction;
a subtracter (4) for getting a difference of signals from the two photodetectors and generating a difference signal;
a filter (6) for removing a wobble frequency component of a wobbled track and generating a groove discontinuity pulse;
a discriminator (12) for detecting a groove discontinuity pulse width and discriminating each synchronization mark, positive mark, and negative mark based on said width to generate a synchronization mark signal, positive mark signal, and negative mark signal; and
a demodulator (14) for generating 1s and 0s according to each positive mark signal and negative mark signal contained between one synchronization mark signal and a next synchronization mark signal.
The invention as described in claim 24 is an address reading method for detecting synchronization marks, positive marks, and negative marks contained in an optical disc as described in claim 1 and accumulating 1 and 0 data obtained from positive marks and negative marks dispersedly contained in one sector block to read said sector block address, comprising:
emitting a laser beam to a track of the optical disc and detecting reflected light by means of two photodetectors separated along the track direction;
getting a difference of signals from the two photodetectors and generating a difference signal;
removing a wobble frequency component of a wobbled track and generating a groove discontinuity pulse;
detecting a groove discontinuity pulse width and discriminating each synchronization mark, positive mark, and negative mark based on said width to generate a synchronization mark signal, positive mark signal, and negative mark signal; and
generating 1s and 0s according to each positive mark signal and negative mark signal contained between one synchronization mark signal and a next synchronization mark signal.
The invention as described in claim 25 is an address reading apparatus for detecting synchronization marks, positive marks, and negative marks contained in an optical disc as described in claim 10 and accumulating 1 and 0 data obtained from positive marks and negative marks dispersedly contained in one sector block to read said sector block address, comprising:
an optical head (2) for emitting a laser beam to a track of the optical disc and detecting reflected light by means of two photodetectors separated along the track direction;
a subtracter (4) for getting a difference of signals from the two photodetectors and generating a difference signal;
a filter (6) for removing a wobble frequency component of a wobbled track and generating a groove bottom offset portion pulse in a negative direction and a groove top offset portion pulse in a positive direction;
discriminators (52, 54, 12) for discriminating each synchronization mark, positive mark, and negative mark based on said groove top offset portion pulse, groove bottom offset portion pulse, and groove bottom offset portion pulse and groove top offset portion pulse pair to generate a positive mark signal, negative mark signal, and synchronization mark signal; and
a demodulator (14) for generating 1s and 0s according to each positive mark signal and negative mark signal contained between one synchronization mark signal and a next synchronization mark signal.
The invention as described in claim 26 is an address reading method for detecting synchronization marks, positive marks, and negative marks contained in an optical disc as described in claim 10 and accumulating 1 and 0 data obtained from positive marks and negative marks dispersedly contained in one sector block to read said sector block address, comprising:
emitting a laser beam to a track of the optical disc and detecting reflected light by means of two photodetectors separated along the track direction;
getting a difference of signals from the two photodetectors and generating a difference signal;
removing a wobble frequency component of a wobbled track and generating a groove bottom offset portion pulse in a negative direction and a groove top offset portion pulse in a positive direction;
discriminating each synchronization mark, positive mark, and negative mark based on said groove top offset portion pulse, groove bottom offset portion pulse, and groove bottom offset portion pulse and groove top offset portion pulse pair to generate a positive mark signal, negative mark signal, and synchronization mark signal; and
generating 1s and 0s according to each positive mark signal and negative mark signal contained between one synchronization mark signal and a next synchronization mark signal.
The invention as described in claim 27 is an address reading apparatus for detecting synchronization marks, positive marks, and negative marks contained in an optical disc as described in claim 15 and accumulating 1 and 0 data obtained from positive marks and negative marks dispersedly contained in one sector block to read said sector block address, comprising:
an optical head (2) for emitting a laser beam to a track of the optical disc and detecting reflected light by means of two photodetectors separated along the track direction;
a subtracter (4) for getting a difference of signals from the two photodetectors and generating a difference signal;
a filter (6) for removing a wobble frequency component of a wobbled track and generating a groove descending-phase inversion part pulse in a negative direction and a groove ascending-phase inversion part pulse in a positive direction;
discriminators (52, 54, 12) for discriminating each synchronization mark, positive mark, and negative mark based on said groove ascending-phase inversion part pulse, groove descending-phase inversion part pulse, and groove descending-phase inversion part pulse and groove ascending-phase inversion part pulse pair to generate a positive mark signal, negative mark signal, and synchronization mark signal; and
a demodulator (14) for generating 1s and 0s according to each positive mark signal and negative mark signal contained between one synchronization mark signal and a next synchronization mark signal.
The invention as described in claim 28 is an address reading method for detecting synchronization marks, positive marks, and negative marks contained in an optical disc as described in claim 15 and accumulating 1 and 0 data obtained from positive marks and negative marks dispersedly contained in one sector block to read said sector block address, comprising:
emitting a laser beam to a track of the optical disc and detecting reflected light by means of two photodetectors separated along the track direction;
getting a difference of signals from the two photodetectors and generating a difference signal;
removing a wobble frequency component of a wobbled track and generating a groove descending-phase inversion part pulse in a negative direction and a groove ascending-phase inversion part pulse in a positive direction;
discriminating each synchronization mark, positive mark, and negative mark based on said groove ascending-phase inversion part pulse, groove descending-phase inversion part pulse, and groove descending-phase inversion part pulse and groove ascending-phase inversion part pulse pair to generate a positive mark signal, negative mark signal, and synchronization mark signal; and
generating 1s and 0s according to each positive mark signal and negative mark signal contained between one synchronization mark signal and a next synchronization mark signal.
The invention as described in claim 29 is an address reading apparatus for detecting synchronization marks, positive marks, and negative marks contained in an optical disc as described in claim 19 and accumulating 1 and 0 data obtained from positive marks and negative marks dispersedly contained in one sector block to read said sector block address, comprising:
an optical head (2) for emitting a laser beam to a track of the optical disc and detecting reflected light by means of two photodetectors separated along the track direction;
a subtracter (4) for getting a difference of signals from the two photodetectors and generating a difference signal;
a filter (6) for removing a wobble frequency component of a wobbled track and generating a groove descending-rectilinear portion pulse in a negative direction and a groove ascending-rectilinear portion pulse in a positive direction;
discriminators (52, 54, 12) for discriminating each synchronization mark, positive mark, and negative mark based on said groove ascending-rectilinear portion pulse, groove descending-rectilinear portion pulse, and groove descending-rectilinear portion pulse and groove ascending-rectilinear portion pulse pair to generate a positive mark signal, negative mark signal, and synchronization mark signal; and
a demodulator (14) for generating 1s and 0s according to each positive mark signal and negative mark signal contained between one synchronization mark signal and a next synchronization mark signal.
The invention as described in claim 30 is an address reading method for detecting synchronization marks, positive marks, and negative marks contained in an optical disc as described in claim 19 and accumulating 1 and 0 data obtained from positive marks and negative marks dispersedly contained in one sector block to read said sector block address, comprising:
emitting a laser beam to a track of the optical disc and detecting reflected light by means of two photodetectors separated along the track direction;
getting a difference of signals from the two photodetectors and generating a difference signal;
removing a wobble frequency component of a wobbled track and generating a groove descending-rectilinear portion pulse in a negative direction and a groove ascending-rectilinear portion pulse in a positive direction;
discriminating each synchronization mark, positive mark, and negative mark based on said groove ascending-rectilinear portion pulse, groove descending-rectilinear portion pulse, and groove descending-rectilinear portion pulse and groove ascending-rectilinear portion pulse pair to generate a positive mark signal, negative mark signal, and synchronization mark signal; and
generating 1s and 0s according to each positive mark signal and negative mark signal contained between one synchronization mark signal and a next synchronization mark signal.
The invention as described in claim 31 is an address reading apparatus for detecting synchronization marks, positive marks, and negative marks contained in an optical disc as described in claim 21 and accumulating 1 and 0 data obtained from positive marks and negative marks dispersedly contained in one sector block to read said sector block address, comprising:
an optical head (2) for emitting a laser beam to a track of the optical disc and detecting reflected light by means of two photodetectors separated along the track direction;
a subtracter (4) for getting a difference of signals from the two photodetectors and generating a difference signal;
a filter (6) for removing a wobble frequency component of a wobbled track and generating a groove descending-rectilinear portion pulse in a negative direction and a groove ascending-rectilinear portion pulse in a positive direction;
a first counter (93) for counting a number of groove descending-rectilinear portion pulses in a negative direction contained in one sector;
a second counter (94) for counting a number of groove ascending-rectilinear portion pulses in a positive direction contained in one sector;
discriminators (95 to 99) for comparing a first count from the first counter and a second count from the second counter and discriminating each synchronization mark, positive mark, and negative mark according to whether the first count is sufficiently high, the second count is sufficiently high, or the first count and second count are substantially equal to generate a positive mark signal, negative mark signal, and synchronization mark signal; and
a demodulator (14) for generating 1s and 0s according to each positive mark signal and negative mark signal contained between one synchronization mark signal and a next synchronization mark signal.
The invention as described in claim 32 is an address reading method for detecting synchronization marks, positive marks, and negative marks contained in an optical disc as described in claim 21 and accumulating 1 and 0 data obtained from positive marks and negative marks dispersedly contained in one sector block to read said sector block address, comprising:
emitting a laser beam to a track of the optical disc and detecting reflected light by means of two photodetectors separated along the track direction;
getting a difference of signals from the two photodetectors and generating a difference signal;
removing a wobble frequency component of a wobbled track and generating a groove descending-rectilinear portion pulse in a negative direction and a groove ascending-rectilinear portion pulse in a positive direction;
counting a number of groove descending-rectilinear portion pulses in a negative direction contained in one sector as a first count;
counting a number of groove ascending-rectilinear portion pulses in a positive direction contained in one sector as a second count;
comparing the first count and second count and discriminating each synchronization mark, positive mark, and negative mark according to whether the first count is sufficiently high, the second count is sufficiently high, or the first count and second count are substantially equal to generate a positive mark signal, negative mark signal, and synchronization mark signal; and
generating 1s and 0s according to each positive mark signal and negative mark signal contained between one synchronization mark signal and a next synchronization mark signal.
The invention as described in claim 33 is an optical disc as described in claim 19, wherein the synchronization mark further has a block mark indicating a sector block starting position.
The invention as described in claim 34 is an optical disc as described in claim 33, wherein said block mark is formed by disposing a discontinuity in the track groove.
The invention as described in claim 35 is an optical disc as described in claim 33, wherein said block mark is formed by locally changing a width of the track groove.
The invention as described in claim 36 is an optical disc as described in claim 33, wherein said block mark is formed by locally changing wobble amplitude.
The invention as described in claim 37 is an optical disc as described in claim 19, wherein each wobble cycle is formed so that the duty ratio differs according to positive data and negative data.
The invention as described in claim 38 is an optical disc as described in claim 19, wherein only one edge of the track groove is wobbled.
(Advantages Over the Related Art)
Meaning other than simply identifying the presence or absence of a modification can be imparted to each groove modification by forming groove modifications of multiple different shapes in a wobble groove. More information can therefore be recorded with fewer groove modifications.
An address reader of simple configuration according to the present invention can also accurately and efficiently read dispersed addresses.